The Volvo 780 brake light utilizes a P21W bulb size for illumination across all recorded vehicle versions. Data for the specified component covers the period from 1987 through 1991.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Volvo 780 uses the P21W bulb across all brake light positions for the 1987-1991 model years.
The P21W is an ECE-standardized bulb type, meaning it conforms to European and international regulations for automotive lighting.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is typical for stop and signal lighting applications.
The P21W is a single-filament bulb, meaning it serves one lighting function rather than combining, for example, stop and tail functions within a single unit.
The BA15s bayonet base on the P21W features a single contact pin, which is the physical interface between the bulb and the vehicle's lamp socket.
Both the standard brake lights and the Center High Mount Stop Light on the Volvo 780 share the same P21W specification across the full 1987-1991 production run.
The BA15s base designation is not interchangeable with the BA15d base, which carries two offset pins. Substituting a BA15d bulb in a BA15s socket is not possible without modification.
Because the P21W is an ECE-standard type, it is widely available in markets outside North America, where SAE-standard bulbs such as the 1156 are more common. The 1156 shares similar wattage and voltage ratings but uses a different base configuration.